In manufacturing semiconductor devices, owing to the recent demands of increased miniaturization and integration, circuit configuration is getting increasingly finer. Also, according to the requirement of forming a metallic film used for an interconnection layer, a burying layer, and a contact layer etc., with a favorable step coverage, CVD (Chemical Vapor Deposition) has been selected.
For example, a single type plasma CVD is utilized in case of depositing Ti film with CVD to be used as a contact layer. In the single type plasma CVD, semiconductor wafers (hereinafter, wafers) each of which is a substrate to be processed is introduced into a chamber one piece at a time, and plasma is generated using, for example, TiCl4 gas as a source gas and H2 gas as a reduction gas, thereby forming Ti film on the wafer disposed on a stage heated to about 400° C.˜700° C.
For the deposition of Ti film by the single type plasma CVD, the method includes a step of repeating a cycle in which a precoating process is performed in the chamber, the deposition of Ti film is continuously performed for hundreds to thousands pieces of wafers, and then, a dry cleaning is performed by using, for example, ClF3 gas (for example, see JP Laid Open No. 2007-165479).
Recently, since a fine patterning process is performed in an etching process prior to the Ti film forming process by the plasma CVD, polymer base (C—F base) residue during the etching process may be remained at the periphery portion (near the bevel) of the back side of the wafer. Also, since the ashing process and the wet cleaning process are performed with a single wafer type, these processes may not be performed sufficiently for the back side of the wafer and the wafer is introduced into the Ti film forming chamber with the polymer residue at the back side of the wafer. The polymer residue at the back side of the wafer are adhered to the high temperature susceptor (specifically to the portion corresponding to the wafer periphery) serving as the wafer stage, and be thickened during the repeated operation of the Ti film forming process, thereby making a microgap between the wafer and the wafer stage. When the high frequency electric power is applied to generate plasma at this state, an abnormal discharge may occur at an area where the microgap is produced, and there is concern that troubles in products or damage in stage may occur.